## I/V Characteristics

##### Created by:

caitlinrjohnston  on March 30, 2012

June 2012

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# I/V Characteristics

 What does the term I/V characteristic mean?It refers to a graph which shows how the current (I) flowing through a component changes as the potential difference (V) across it increases.
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#### Definitions

What does the term I/V characteristic mean? It refers to a graph which shows how the current (I) flowing through a component changes as the potential difference (V) across it increases.
If the graph has a shallower gradient, how is the resistance changed? It is greater.
What does a curve show? That the resistance is changing.
What does the I/V characteristic look like for a metallic conductor? A straight line
What does the straight line graph I/V characteristic of metals tell you? That the current is directly proportional to the voltage, at a constant temperature, and therefore the metal conductor is ohmic, they have a constant resistance provided their temperature doesn't change.
what does a filament lamp's graph look like and why? Relate this to ohms law. A curve, because the metal wire in the lamp gets hot. Therefore ohms law cannot be applied here and the current and voltage are not proportional. The resistance increases as the temperature increases.
How does the temperature affect the charge carriers?1) Charge is carried through metals by free electrons in a lattice of positive ions
2) Heating up the metal doesn't affect how many atoms there are but it does affect how easy it is for them to move around. The ions vibrate more when heated, so the electrons collide with them more often, loosing energy.
How are semi-conductors used in sensors?They are no where near as good as conducting electricity as metals, as there are fewer charge carriers available. However, if energy is supplied to the semi-conductor, more charge carriers are often released. This means that they make excellent sensors for detecting changes in thei environment.
What are the three semi-conductors I need to know about? Thermistors, LDRs and Diodes
What does the resistance of a thermistor depend on? Temperature
Describe the relationship between temperature and resistance in a NTC (Negative Temperature Coefficient) thermistor. Resistance decreases as the temperature goes up
Explain the relationship between temperature and resistance in a NTC (Negative Temperature Coefficient) thermistor. Warming the thermistor gives more electrons enough energy to escape from their atoms, this means there are more charge carriers available so the resistance is lower.
What does the resistance of an LDR depend on? Light intensity
Describe the relationship between light intensity and resistance. The greater the intensity of light shining on an LDR the lower its resistance
Explain the relationship between light intensity and resistance. Light provide the electrons with more energy to break free from their atoms. There are therefore more charge carriers, and a lower resistance.
What is special about diode resistors? They only let current flow in one direction.
What is the direction in which the current is allowed to flow called? Forward Bias
What is the threshold voltage needed for the diode to conduct? 0.6V in the forward direction
Describe the resistance and current in the reverse bias. Resistance - very high
Current - very tiny

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